Steel.



3o being taken to keep the amount of manga- I .IEatented August 4, 1903.

PATENT- GFFICE.

ROBERT ABBOTT HADFIELD, OF SHEFFIELD, ENGLAND.

STEEL.

$PECIFICATION forming part of Letters Patent N 0. 735,365, dated August4, 1903.

A pplication filed March 9, 1898. Serial No. 674,497. (No specimens.)

To all whom it may concern:

Be it known that I, ROBERT ABBOTT HAD- FIELD, a subject of the Queen ofGreat Britain, residing at Sheflield, county of York, England, haveinvented an Improvement in Processes of Making Chromium-Nickel Steel, ofwhich the following description is a specification.

This invention relates to the manufacture at a comparatively low cost ofhard steel possessing superior qualities and which can be cast, rolled,and forged like other hard steel, having special susceptibility tohardening with less liability to water-cracking than usual-as, forinstance, frequently occurs with ordinary steel-the steel to behereinafter described being particularly suitable for use in theproduction of articles of comparatively large sectional area thatrequire to be hardened in the mass-that is to say, practicallythroughout their section.

.One exceedingly useful employment of my novel steel is in theproduction of projectiles possessing great strength and penetrativepowers and specially suitable for armor-pierc- -ing and like purposes.

In carrying out my invention I add to a suitable basis of iron, say,about 0.7 5 per cent. to one per cent. of carbon, two per cent. ofchromium, and two per cent. of nickel, care nese that may be present atleast under 0.3 per cent. and preferably as much lower as possible, as Ihave found in my experiments that the presence of manganese much inexcess of the quantity mentioned causes watercracking when the steel ishardened. The percentages of carbon, cl1romium,'and nickel may be variedto some extent from those hereinbefore mentioned, provided the resultingproduct is nearly free from or low in manganese and capable of beingreadily hardened. Thus the carbon might vary from 0.60 per cent. up to1.75 per cent, the chromium from about 0.25 per cent. up to five percent, and the nickel from about 0.25 per cent. up to seven per cent. Ihave, however, obtained the best results for articles of comparativelylarge mass with the proportions first mentioned, manganese beingpractically absent in theresultantproduct. A solidifying agentmaybeadded to the steel, preferably in a the silicon may vary inquantity up to about 2.50 per cent, though preferably for most purposessmaller quantities-say of aboutO. 30

per cent. are suflicient-while the aluminium may vary up to about 0.20per cent, but preferably for most purposes not more than 0.10

per cent. will be necessary.

A suitable basis of iron for making my improved steel is decarbonizediron, produced by any suitable steel-making process and as free aspossible from manganese. The carbon, chromium, nickel, and thesolidifying agent may be added in various forms. For example, thecarbonizing physic may be in the form of a suitable carbonaceousmaterialas, for instance, white iron of good pure quality, low in sulfurand phosphorus, and practically free from manganese. The chromium ornickel may be added in the metallic form or in the form of ferrochromiumand ferroniekel, respectively. Aluminium may be added in the matallicstate or in the form of ferroaluminium and the silicon in the bytreatment in the ordinary way in an openhearth furnace, care being takenin either case to eliminate practically the whole of the carbon,manganese, and silicon it may con-. tain. To the molten iron thusobtained I add the carbonizing physio, chromium, and

nickel, as hereinbefore described, and preferably' also the solidifyingagent-that ,is, aluminium and silicon, either or both. The manner ofmaking these additions is of the greatest importance in producing steelof special high quality, and I proceed as follows, viz: The carbonizingphysio is melted in crucibles or in a furnace which is not subject tooxidizing influence, and the molten physio is run into a ladle. Forexample, a furnace may be used with a basic lining, such as dolomite, ormagnesite, or magnesia, or mixtures of these in which the constituentelements of the alloy are not oxidized. Upon the physio the decarbonizediron, as described, is then poured. The addition of. the physic in thefurnace itself is objectionable because oxidizing influences are at onceat work, and consequently steel of such uniformity as I produce cannotbe obtained. It is extremely important in order to obtain a satisfactoryresult that the various additions be made with accuracy,'and for thisreason they (the additions) should not be made to the molten iron Whilethe latter is in the converting vessel or furnace, as by such procedureit is difficult to insure that the resulting steel shall contain thedesired exact proportions of the added substances and shall be ofuniform quality.

; Toobviate this difficulty, I prefer to run successively into a ladleor vessel carried by a ence is in many ways very deleterious.

, manganese harmful.

suitable weighing-machine, such as a Denison weighing-machine or aplatform weighing-machine, the desired amounts of carbonizing physio,chromium, nickel, and the solidifying agent, each in a suitable form orcondition, such as hereinbefore described, and in a molten state. Thedesired weights of the several substances, preferably previously meltedin crucibles, are thus ascertained in a ready and very exact manner.Into the weighed molten contents of the ladle while the latter iscarried by the weighing-machine is then run, preferably direct from thefurnace, so much of the molten iron as will increase the weight of thecontents of the ladle to that of the required quantity of my specialsteel, which is then either run off into ingots, which can be afterwardforged into articles of desired shape, or it is poured into suitablemolds to produce castings.

I have found the commonly-accepted idea that manganese is necessary insteel is to a large extent erroneous, and,in fact, its pres In makingspecial highquality steel-that is, hard steels containing, say, 0.70 toone per cent. of carbonI find that the lower the manganese is kept thebetter the product; but when the material is not required to possesshardness primarily'. 6., natural hardness or capacity for subsequenthardeningthe advantage to be gained is not so great, as I believe thatonly in the presence of carbon is the In other words, manganese may notbe objectionable in mild steelssayunder about 0.35 per cent. carbonhe?cause in such cases, and they probably repreaction as a carbid ofmanganese when carbon is present it is most harmful where the specialqualities of hardness and toughness are requisite, believing that thesequalities cannot be developed if manganese is present in quantity, say,over 0.25 per cent. It is to be borne in mind, however, that I amnotreferring to large percentages, such as in I-Iadfield manganese steelalloys containing over two per cent. up to twenty per cent. manganese,of which I am the inventor and which come under an entirely differentcategory.

Hitherto, so far as I am aware, it has not been known that sound ingots,sound both as regards freedom from unsoundness-that is, honcycombedandsound as regards forgingthat is, free from cracks or other forgingdefects-could be obtained without the presence of manganese,particularly if silicon or aluminium,orboth,be used; but,as hereinbeforeset forth, I have discovered this fact, and that with sufficient siliconor aluminium, or both, no manganese is required, while the resultantproduct can be rolled and forged like other hard steels and hardened andtempered readily, with the cracking not only no more but actually lessthan with the most expensive crucible steels. I find that withpractically no manganese the steel, while hardening equally as well asheretofore, is much tougher and shows a better-looking fracture, all ofwhich goes to show that the absence of manganese has prevented theformation of the very obj ectionable brittle carbid of manganese.

In the production of high-power projectiles from my improved steel thelatter is either cast or forged into suitable shape, and in the formercase the steel is run off from the ladle into molds, preferably iron orpartly iron and partly sand and provided with suitable cores when theprojectiles are to be formed with a bursting-chamber. Solid projectilesmay be cast either point or base upward; but in casting chamberedprojectiles I prefer to cast the lower or ogival part of the projectilein an iron mold, it being possible to thereby cast thinner-walled shellsthan could be so successfully accomplished if cast entirely in sand orentirely in iron molds. After removal from .the mold the projectile ispreferably annealed by heating to a suitable annealing temperature-sayabout 1,600 Fahrenheit in a furnaceand then permitting it to coolslowly. The sinking or feeding head is out from the casting in anysuitable manner, and any necessary machining of the projectile can beperformed. The projectile is then hardened, preferably at its point andshoulder portions, and for this purpose these portions are heated to asuitable temperature say from about 1,500 to 1,700 Fahrenheit and thenquickly dipped point downward ile is to be forged, an ingot of the steelis Y forged approximately to shape and then a11- nealed, machined, boredout, if necessary, andhardened, the annealing and hardening beingeifected in the'manner described relative to cast projectiles.

As before stated, the presence of manganese in hard steel tends torender the steel brittle when it is hardened in a similar manner to butto a less degree than phosphorus, and for this reason I regard manganeseas a deleterious element in hard steel as sulfur and phosphorus areregarded deleterious in iron and steel, and manganese therefore is anelement the presence of which should be avoided as much as possible.

Having fully described my invention, What I claim, and desire tosecureby Letters Patent, is l l. The process of making steel free from or lowin manganese, which consists in decarbonizing and demanganizing iron,and adding thereto a carbonizing agent, chromium and nickel, and asolidifying agent.

2. The process of making chromium-nickel steel, which consists inbringing together and mixing molten decarbonized, demanganized anddes-iliconized iron, a carbonizing agent in a molten state, and moltenchromium, nickel, and a solidifying agent.

3. The process of making chromium-nickel steel, which consists inbringing together and mixing molten decarbonized, demanganized anddesiliconized iron, a carbonizing agent in a molten state, and moltenchromium and nickel.

4. The process of making chromium-nickel steel, which consists inbringing together and mixing in a molten state decarbonized,demanganized and desiliconized iron, acarbonizing agent, chromium,nickel and a solidifying agent, in a ladle or other vessel, and weighingeach element in its molten condition, whereby the weight and proportionof each can be readily and accurately controlled.

5. In the process of manufacturing chromium-nickel steel, successivelyintroducing in a molten state a carbonizing agent, chromium, nickel, asolidifying agent, and decarbonized, demanganized and desiliconized ironinto a suitable vessel, the several ingredients being weighed in theirmolten condition, as they are successively introduced to the vessel,whereby the exact weight and proportion of each ingredient may beaccurately determined.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

ROBERT ABBOTT l-IADFIELD.

W itnesses GEORGE II. HEMsoLL, HOWARD MARTIN.

